Lead frame design to improve reliability

ABSTRACT

An electronic device package  100  comprising a lead frame  150  having at least one lead  110  with a notch  205 . The notch includes at least one reentrant angle  210  of greater than 180 degrees and the notch is located distal to a cut end  1010  of the lead.

TECHNICAL FIELD

This application is directed, in general, to electronic device packagesand their method of manufacture and, more specifically, to lead framedesigns for device packages.

BACKGROUND

Wire-bonded lead frame packages often incorporate metal plating on thepackage's leads to provide a surface that is compatible with the wirebonding. In some cases, however, these packages havepoorer-than-expected reliability.

SUMMARY

One embodiment of the disclosure is a method of manufacturing anelectronic device package. The method comprises providing a lead frame,the lead frame having a plurality of leads attached thereto. The methodalso comprises forming a notch in at least one of said leads. The notchincludes at least one reentrant angle of greater than 180 degrees. Thenotch is located distal to a pre-defined separation region of the lead.

Still another embodiment of the disclosure is an electronic devicepackage. The package comprises a lead frame having at least one leadwith a notch. The notch includes at least one reentrant angle of greaterthan 180 degrees and the notch is located distal to a cut end of thelead.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments can be understood from the following detaileddescription, when read with the accompanying figures. Various featuresmay not be drawn to scale and may be arbitrarily increased or reduced insize for clarity of discussion. Reference is now made to the followingdescriptions taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A presents a plan view of an example lead frame of at a stage ofmanufacture in accordance with the disclosure;

FIG. 1B presents a plan view of an example design layout for an examplelead frame of the disclosure;

FIG. 2 presents a plan view of an example lead at a stage of manufacturein accordance with the disclosure;

FIG. 3 presents a perspective view of an example lead at a stage ofmanufacture in accordance with the disclosure;

FIG. 4A presents a plan view of an example lead at a stage ofmanufacture in accordance with the disclosure;

FIG. 4B presents a plan view of an example lead at a stage ofmanufacture in accordance with the disclosure;

FIG. 4C presents a plan view of an example lead at a stage ofmanufacture in accordance with the disclosure;

FIG. 5 presents a perspective view of an example lead and lead frame ata stage of manufacture in accordance with the disclosure;

FIG. 6 presents a perspective view of an example lead and lead frame ata stage of manufacture in accordance with the disclosure;

FIG. 7 presents a plan view of an example lead frame and electronicdevice package at a stage of manufacture in accordance with thedisclosure;

FIG. 8 presents a plan view of an example lead frame and electronicdevice package at a stage of manufacture in accordance with thedisclosure;

FIG. 9 presents a plan view of an example lead frame and electronicdevice package at a stage of manufacture in accordance with thedisclosure;

FIG. 10 presents a perspective view example electronic device package ofthe disclosure.

DETAILED DESCRIPTION

Certain metals used to plate lead frames can be susceptible toelectrochemical migration when an external voltage bias is appliedacross two or more leads. Electrochemical migration can cause shortcircuits in the lead frame package, and, therefore reduce thereliability of the package. It is therefore desirable to prevent havingsuch metals exposed in the finally assembled package. For certain leadframe packages, however, it is possible for these plated metals tobecome freshly exposed when the ends of the leads are severed from thelead frame. Nevertheless, because the ends of the leads are designed tobe passivated with solder (e.g., Pb-containing solder) when attached tothe printed circuit board (PCB), any freshly exposed plated metal on theleads prior to exposure to solder is not expected to pose a reliabilityrisk.

Contrary to these expectations, as part of the present disclosure, wediscovered that the plated metal that is freshly exposed during thesevering of leads can become the sites of the rapid growth of metalformations, commonly referred to as “whiskers.” Moreover, the whiskerscan rapidly form and grow even without the application of an externalvoltage bias, and, can occur prior to PCB and Pb-solder attachment.

Once formed, metal whiskers can cause device failure in severaldifferent ways. Metal whiskers may not be passivated by the Pb-solderduring PCB attachment, and therefore may continue to grow, or, undergoelectrochemical migration, which of which can result in a short circuitthat causes device failure. Metal whiskers may fracture and separatefrom a lead, e.g., as a result of handling during PCB assembly, and landon part of the PCB that is not exposed to Pb-solder. Subsequent handlingcould dislodge the whisker which could then cause a short circuitresulting in device failure. Metal whiskers may fracture and separatefrom a lead and contaminate the test hardware used to test device PCBassembly and packaging, thereby causing the test hardware to operateincorrectly.

The present disclosure mitigates metal whisker formation by preventingthe metal plate from being freshly exposed when the leads are severed.We discovered that metal plating can unintentionally occur underneath aplating mask. Consequently, a thin layer of metal plating can extendunderneath the plating mask to the region of the lead that is designedto be cut when the leads are severed from the lead frame. We furtherdiscovered that introducing a notch in a lead in the vicinity of wherethe plating mask overlaps with the lead can help prevent the metalplating from extending underneath the plating mask. Because there is nometal plating in the region of the lead that is cut when the leads aresevered from the lead frame, metal whiskers are not formed.

During plating, there is a high electric field in the vicinity of thenotch, which results in additional metal plating in the vicinity of thestep up to the leading edge of the step in the direction of the platingmask. This in turn, helps to prevent metal plating under the platingmask. Because plating underneath the plating mask is prevent, there isno metal plating in the region of the lead that is designed to be cut.Consequently, there is no freshly exposed plated metal when the leadsare severed, and therefore, whisker formation is mitigated.

One embodiment of the present disclosure is a method of manufacturing anelectronic device package. FIGS. 1-9 present perspective, plan andcross-sectional views of an example device package 100 at selectedstages of manufacture.

FIG. 1A presents a plan view of an example lead frame 105 which isprovided as part of the method. The lead frame 105 has a plurality ofleads 110. One of ordinary skill in the art would be familiar with theprocesses to manufacture a variety of lead frames types. For instance,one skilled in the art would be familiar with techniques (e.g.,photolithography) to define a design layout 115 (FIG. 1B) on a metalsheet 120 (e.g., copper or aluminum), and, how to remove parts of themetal sheet 120 outside of the design layout 115 (e.g., stamping oretching) to form the lead frame 105 and leads 110 (FIG. 1A).

In some cases, as depicted in FIG. 1A, the lead frame 105 can beconfigured as a quad flat pack (QFP) type lead frame. Non-limitingexamples of other configurations of the lead frame 110 include fusionqual type lead frames, lead frames appropriate for plastic dual in-lineintegrated circuit packages (PDIP), small outline integrated circuits(SOICs), thin QFPs (TQFPs), low profile QFPs (LPQFPs), small shrinkoutline plastic packages (SSOP), thin SSOPs (TSSOPs), thin verysmall-outline packages (TVSOPs), or, other types of lead-containing leadframe packages.

FIG. 2 presents a higher magnification plan view (corresponding thestructure shown within region 2 in FIG. 1) to show the detailed featuresfor one of the plurality of leads 110 of the example lead frame 105 inFIG. 1. FIG. 3 presents a perspective view corresponding to the planview of FIG. 2, e.g., along view line A-A, in FIG. 3. For this exampleembodiment a cross-section view along view line B-B would besubstantially the same as the plan view shown in FIG. 2. In otherembodiments, however, the leads 110 may be asymmetrically dimensionedalong these two view lines.

FIGS. 2 and 3 show the package 100 after forming a notch 205 in at leastone of the plurality of leads 110. The notch 205 includes at least atleast one reentrant angle 210 of greater than 180 degrees. The notch 205is located distal to a pre-defined separation region 215 of the lead110.

In some cases, the notch 205 can be formed as part of the process tomanufacture the lead frames 105. For instance, the notch can be includedin the design layout 115 formed on the metal sheet 120 and then formedas part of removing parts of the metal sheet outside of the designlayout 115 (FIG. 1B). In other cases a lead frame 105, prefabricatedwith notch-less leads 110, is further processed to form the notch 205 inthe at least one lead 110. For instance, one or more of the leads 110can be subject to mechanical or laser cutting, similar to that used tocut the metal sheet 120, to form the notch 205.

The term reentrant angle 210 as used herein refers to an interior angleon an outer surface 220 of the lead 110 where the apex 225 of the angle210 faces into the interior of the lead 110. The term pre-definedseparation region 215 as used herein refers to that portion of the lead110 that is designed to be cut in order to isolate the lead 110 fromother parts of the lead frame 105 (e.g., mounting portion 125, FIG. 1A).

In some preferred embodiments, to maximally reduce the likelihood ofwhisker formation, it is preferable to form a notch 205 in each one ofthe leads 110. Nevertheless, it is still possible that that a notch-lesslead, adjacent to one or more notched leads, could have reduced whiskerformation. For instance the high electric field associated with thenotches in the notched leads could cause reduced metal plating in thepre-defined separation region 215 of an adjacent notch-less lead.

To further maximally reduce the likelihood of whisker formation, asillustrated in FIG. 3, it is also preferable for the notch 205 tocircumscribe lateral dimensions (e.g., a thickness 310 and width 315) ofthe lead 110 which are perpendicular to a long dimension 320 of the lead110. That is, the notch 205 goes all the way around the lead 110,thereby providing a high electric field strength that is uniform all theway around the notch 205 of the lead 110 when a bias voltage is appliedto the lead frame 105. For example, as shown in FIG. 3, when the lead110 has a rectangular shape, the notch 205 can be formed in both thethickness and width dimensions 310, 315. Or, when the lead 110 iscylindrically-shaped, the notch 205 can be in the cylindrical dimensionperpendicular (not shown) to the long dimension 320 of the lead 110.

There can still be cases, however, when forming the notch 205 on onlyone side or two sides of the lead 110 can still help to deter whiskerformation. For instance, forming notches 205 in the thickness dimension310 and covering the width dimension 315 with a mask can deter metalplating in the pre-defined separation region 215, and hence reduce thechances of whisker formation. For instance, in some cases, the highelectric field associated with the notch 205 may draw a sufficientamount of current to the notch 205 so as to reduce metal plating in thepre-defined separation region 215, even though the notch 205 is onlypresent on one side of the lead 110. Additionally such configuration canbe advantageous when having the notch 205 circumscribe the lateraldimensions 310, 315 would mechanically weaken the lead 110 to anexcessive degree.

As illustrated in FIG. 2, in some embodiments, forming the notch 205includes forming an opening 230 in the lead 110. The opening 230protrudes inward relative to an outer surface 220 of the lead 110. Inother embodiments, the notch can be formed so as to protrude outward.FIG. 4A presents a plan view analogous to that shown in FIG. 2, showingan example embodiment of a notch 205 formed by the method where thenotch 205 has a step 410 that protrudes outward from the outer surface235 of the lead 110. As illustrated, the rectangular-shaped step 410 hastwo reentrant angles 210 in the plane of the lead 110 that is depictedin FIG. 4A.

FIG. 4B-4C show plan views analogous to the view shown in FIG. 2, ofother example notch shapes. For instance, as shown in FIG. 4B, the notch205 can include a wedge-shaped opening 230, here shown with a singlereentrant angle 210. For instance, as shown in FIG. 4C, the notch 205can include an opening 230 and a step 410, e.g., on different sides ofthe lead 110. As further illustrated in FIG. 4C, to further increase thestrength of the electric field associated with the notch 205, additionalreentrant angles 210 can be formed by having one or moresecondary-openings 420 within the opening 230 or within the step 410 ofthe notch 205. Based on the present disclosure one skilled in the artwould understand how the notch could be formed with a variety of openingor step shapes and combinations thereof.

The method can further include masking portions of the lead frame inpreparation for electroplating. FIG. 5 presents a perspective viewanalogous to that shown in FIG. 3, showing the lead frame 105 afterbeing placed between first and second plating mask layers 510, 515. Asemi-transparent view of the mask layers 510, 515 is presented so thatunderlying structures of the lead frame 105 are visible. In some casesthe mask layers 510, 515 are composed of a rigid insulating materialsuch as a hard plastic or rubber. To help prevent metal plating fromdepositing under the mask layers 510, 515 a proximal edge 520 (e.g., theedge proximal to the center of the lead frame 105) of the notch 205 ispreferably adjacent to an outer edge 525 of at least one of the, andmore preferably both, edges 525, 527, of the plating mask layers 510,515. For example, in some preferred embodiments, a mismatching distance530 between the proximal edge 520 and the edges 525, 527, of the platingmask layers 510, 515 is less than about 10 percent of a total length 535of the notch 205. Additionally, to facilitate metal plating in theregion of the notch 205 a distal edge 540 of the notch 205 is notcovered by the plating mask layers 510, 515.

FIG. 6 shows the lead frame 105 of FIG. 5 after electro-depositing ametal plate 610 (e.g., silver plating) on portions the lead 110 notcovered by the first and second plating mask layers 510, 515. Again,semi-transparent views of the mask layers 510, 515 and metal plate 610are presented so that underlying structures are visible.

One skilled in the art would be familiar with electro-plating processesto deposit the metal plate 610. For instance, in some cases,electro-depositing the metal plate 610 includes placing the lead frame105 and plating mask layers 510, 515 in a metal plating solution andapplying a voltage bias to the lead frame 105. For example in someembodiments, the lead frame 105 and mask layers 510, 515 are placed in ametal plating solution containing silver cations, and a negative voltageof about −0.9 Volts or greater is applied to the lead frame 105 untilthe desired thickness 625 of metal plating 610 is obtained. In somecases the voltage bias applied to the lead frame 105 is in a range ofabout −1 to −25 Volts.

Because electroplating is used, metal plate formation is driven by thestrength of the electric field on the lead's surface. Due to thepresence of the reentrant angle or angles 210 (FIG. 2) the electricfield in the vicinity of the notch 205 will be higher than on otherregions of the lead 110. Therefore, a relatively larger amount ofelectric current goes to the notch 205 as compared to other portions ofthe lead 110. This, in turn, will tends to draw more metal ions to thenotch 205, and thereby prevent, or at least reduce, metal ions fromplating in a proximal region 630 of the lead 110 (relative to thecentral portion of the lead frame 105) covered by the plating mask layer510, 515. For example, due to the high current in the vicinity of thenotch 205, a first thickness 620 of the metal plate 610 located directlyover the notch 205 is greater than a second thickness 625 of the metalplate 610 located over a terminal portion 640 of the lead 110 that isdistal to the notch 205. As noted above, this is in contrast to a leadframe having only notch-less leads, where some metal ions can beelectroplated under the mask layers 510, 515 (FIG. 5) and in thepre-defined separation region 215.

FIG. 7 shows a lower magnification plan view of the lead frame 105 ofthe package 100 analogous to that shown FIG. 1A, after performing themethod steps described in the context of FIGS. 2-6, and after removingthe lead frame 105 from between the mask layer 510, 515, following thedeposition of the metal plate 610. FIG. 7 illustrates an embodiment inwhich a plurality of leads 110 were treated according to the methodsteps described in the context of FIGS. 2-6. The notches 205 (FIG. 2) ofthe leads 110 are covered by the metal plating 610, and, due to thepresence of the notch 205, the metal plating 610 is distal to thepre-defined separation region 215.

FIG. 8 show the package 100 of FIG. 7, after attaching an electronicdevice 810 to the device mounting portion 125 of the lead frame 105 aspart of the package's 100 manufacture. For instance, the electronicdevice 810 comprising one or more integrated circuits can be bonded tothe mounting portion 125 using an adhesive glue.

FIG. 8 further shows the package 100 after bonding a wire 830 (e.g.,gold wire) from a landing pad 840 of the electronic device 810 to theportion of lead 110 covered with the metal plate 610. The wire 830facilitates the electrical interconnection of the electronic device 810to other devices (not shown) of, or external to, the package 100.Preferably, a plurality of wire bonds are formed between the landingpads 840 and leads 110, but for clarity, only a few connections aredepicted.

FIG. 8 also shows the package 100 after covering the electronic device810 and the mounting portion 125 of the lead frame 105 with aninsulating mold 850. For instance, a fluid mold 850, (e.g., organicresin or a ceramic material) can be deposited or cast-molded around thedevice 810 and mounting portion 125, and then allowed to solidify. Themold 850 can protect the device 810 from exposure damaging environmentsand can mechanically stabilize the various components of the package100.

FIG. 9 shows the package 100 of FIG. 8 after severing the leads 110 fromthe device mounting portion 125 of the lead frame 105 by cutting withinthe pre-defined separation regions 215 of the leads 110. Severing can beaccomplished by mechanical sawing, laser cutting or other procedureswell know to those skilled in the art. Similar procedures may beperformed simultaneous, or in separate steps, to sever other portions ofthe lead frame 105, such as handling bars or other support structures(now shown).

Another embodiment of the present disclosure is an electronic devicepackage. Any of the method steps described in the context of FIGS. 1-9could be used to provide the device package 100. FIG. 10 shows aperspective detailed view, analogous to the views shown in FIGS. 3, 5,and 6, of an example package 100 of the disclosure. For clarity, thesame reference numbers are used to label features that are common to theembodiments of FIGS. 1-9. For clarity, the metal plate 610 is depictedas semi-transparent, and, the mold 950 (FIG. 9) is not depicted. FIG. 10shows the example package 100 after performing the steps described inthe context of FIGS. 1-9. In other embodiments, however, the package 100may comprise the lead frame 105 prior to any one, or all, of the methodsteps described in the context of FIGS. 5-9.

As shown in FIG. 10, the electronic device package 100 comprises a leadframe 105 having at least one lead 110 with a notch 205 that includes atleast one reentrant angle 210 (FIG. 2) of greater than 180 degrees. Thenotch 205 is located distal to a cut end 1010 of the lead 110, e.g., anend 1010 of the lead 110 severed from other portions 1020 of the leadframe 105 such as described in the context of FIG. 9 (e.g., the mountingportion 125, FIG. 8).

In some embodiments, each of a plurality of leads 110 of the lead frame105 includes the notch 205 (FIG. 2). In some embodiments, the notch 205circumscribes lateral dimensions 310, 315 of the lead 110, the lateraldimensions 310, 315 being perpendicular to a long dimension 320 of thelead (FIG. 3). For some embodiments, the notch 205 can include arectangular-shaped opening 230 in a outer surface 220 of the lead 110and have at least two reentrant angles 210 (FIG. 2). In otherembodiments, however, the notch 205 can include a wedge-shaped opening,a step structure 410 that protrudes outward from the surface 220, orcombinations thereof, and, the notch 205 can have one or more reentrantangles 210 (FIGS. 4A-C). Based on the present disclosure, one skilled inthe art would appreciate the variety of other shapes that the notch 205could have in order to promote having a high electric field strength inthe notch region, as discussed elsewhere herein.

The dimensions of the notch 205 reflect a balance between severalfactors. The notch's size should be sufficiently large to promote a highelectric field strength in the vicinity of the notch 205. However thenotch's size should be small enough to leave the lead 110 withsufficient mechanical strength to undergo the manufacturing steps andend-use handling without breaking. For instance, too large an opening230 could render the lead 110 too fragile to handle during the package'smanufacture or end-use. The notch's size should be sufficiently large tobe conducive to controlling the notch's manufacture so that thesame-sized notch is reproducibly formed among the leads of a singlepackage, or between packages.

In some preferred embodiments, the notch has an opening with a depthinto the lead which does not exceed about 25 percent of a total lateraldimension of the notch-less portions of the lead. For instance, as shownin FIG. 10, the depth 1020 of the notch's 205 opening 230 in the widthdimension 310 (FIG. 3) preferably does not exceed about 25 percent ofthe lead's total width 1025. Preferably, the depth 1030 of the notch'sopening 230 in the thickness dimension 315 (FIG. 3) also does not exceedabout 25 percent of the lead's total thickness 1035. Consequently, fornotches 205 that circumscribe the lateral dimensions 310, 315 (e.g. FIG.10) of the lead 110, not more that about 50 percent of the lead's width1025 or depth 1030 (e.g., up to 25 percent on each side) is removed toform the opening 230 of a notch 205. In some preferred embodiments, thedepth 1020, 1030 of the opening 230 ranges from about 5 to 25 percent,and more preferably about 10 to 15 percent, of the total lateraldimensions 310 315 (e.g., the total width 1025 and total thickness 1035)of the lead 110.

For example, consider a lead 110 that has a total width 1025 and totalthickness 1035 that are each about 0.4 mm in notch-less portions of thelead 110. The depth of the opening 230 (e.g., width depth 1020 andthickness depth 1030) can be 0.1 mm on each side of the lead 110.Consider a lead 110 with a smaller total width and thickness 1025, 1035(e.g., about 0.1 mm). The lead 110 can have a smaller opening 230 (e.g.,depth of the 1020, 1030 of about 0.01 mm) to preserve the lead'sstrength.

In some embodiments, it is also advantageous for the opening 230 to belong so as to avoid the electric field from bridging across the notch205 and thereby reduce the strength of the field in the vicinity of thenotch 205. It is also desirable however for the opening's length 535 notto be so long as to cause the lead 110 lose stability or to not having ahigh field throughout the entire length of the notch 205. For instance,as shown in FIG. 10, in some preferred embodiments, the opening 230 hasa length 535 equal to about 1.5 to 2.5 times the depth 1020, 1030 of theopening 230. For example consider again a lead 110 wherein the totalwidth 1025 and thickness 1035 are each about 0.4 mm. If the depth 1020,1030 of the notch's opening 230 was about 0.04 mm, then the length 535of the opening preferably ranges from about 0.06 mm to 0.08 mm.

As further illustrated in FIG. 10 a terminal portion 640 of the lead 110that is distal to the notch 205 and the notch 205 itself are preferablyboth covered with a metal plate 610. For instance, in some embodiments,the 110 lead comprises, or in some cases, consists essentially of,copper (e.g., 99 wt % copper or more) and the metal plate 610 comprises,or in some cases, consists essentially of, silver (e.g., 99 wt % or moresilver). A first thickness 620 the metal plate 610 located directly overthe notch 205 is greater (e.g., from about 10 to 100 percent greater)than a second thickness 625 of the metal plate 610 located directly overthe terminal portion 630 of the lead 110 (FIG. 6). For example, in somecases, when the second thickness 620 of metal plate 610 equals about 50microns, then the first thickness 620 can be about 55 to 100 microns.

As illustrated in FIG. 9, the package 100 can further include anelectronic device 810 mounted to a mounting portion 125 of the leadframe 110. The mounting portion 125 is separated from the lead 110 or(leads 110). A portion of the lead proximal 640 to the mounting portionis substantially free of metal plating (e.g., the first thickness 620the metal plate 610 is less than about 1 micron). The package 100 canalso include wires 830 bonded from landing pads 840 of the electronicdevice and to a metal plate 125 covered portion of the lead 110 (e.g.,the notch 205, the terminal portion 630 or both). The package 100 canalso include an insulating mold 850 covering the electronic device 810and the mounting portion 125 of the lead frame 110.

Although some embodiments of the disclosure have been described indetail, those of ordinary skill in the art should understand that theycould make various changes, substitutions and alterations herein withoutdeparting from the scope of the disclosure.

1. An electronic device package, comprising: a lead frame having atleast one lead with a notch that includes at least one reentrant angleof greater than 180 degrees and said notch is located distal to a cutend of said lead, wherein said notch goes all the way around lateraldimensions of said lead that are perpendicular to a long dimension ofsaid lead and a terminal portion said lead that is distal to said notch,and said notch, are both covered with a metal plate.
 2. The package ofclaim 1, wherein each of a plurality of leads of said lead frameincludes said notch.
 3. The package of claim 1, wherein said notchincludes a rectangular-shaped opening in a plane of said lead and saidnotch has at least two of said reentrant angles.
 4. The package of claim1, wherein said notch has an opening with a depth into said lead whichdoes not exceed 25 percent of a total lateral dimension of said lead. 5.The package of claim 1, wherein said opening has a length equal toabout
 1. 5 to 2.5 times said depth of said opening.
 6. The package ofclaim 1, wherein a first thickness of said metal plate located directlyover said notch is greater than a second thickness of said metal platelocated directly over said terminal portion of said lead.
 7. The packageof claim 1, further including: an electronic device mounted to amounting portion of said lead frame, wherein said mounting portion isseparated from said lead and a portion of said lead proximal to saidmounting portion is substantially free of metal plating; wires bondedfrom landing pads on said electronic device to a metal plate coveredportion of said lead; and an insulating mold covering said electronicdevice and said mounting portion of said lead frame.
 8. An electronicdevice package, comprising: a lead frame having at least one lead with aregion of reduced cross-section located distal to a cut end of saidlead, the region of reduced cross-section comprising at least onereentrant angle of greater than 180 degrees, the region of reducedcross-section circumscribing lateral dimensions of said lead that areperpendicular to a long dimension of said lead, and a terminal portionof said lead that is distal to said region of reduced cross-section, andsaid region of reduced cross-section, are both covered with a metalplate.
 9. The package of claim 8, wherein each of a plurality of leadsof said lead frame includes said region of reduced cross-section. 10.The package of claim 8 wherein said region of reduced cross-sectionincludes a rectangular-shaped opening in a plane of said lead and saidregion of reduced cross-section has at least two of said reentrantangles.
 11. The package of claim 8, wherein said region of reducedcross-section has an opening with a depth into said lead which does notexceed 25 percent of a total lateral dimension of said lead.
 12. Thepackage of claim 8, wherein said opening has a length equal to about 1.5to 2.5 times said depth of said opening.
 13. The package of claim 8,wherein a first thickness of said metal plate located directly over saidregion of reduced cross-section is greater than a second thickness ofsaid metal plate located directly over said terminal portion of saidlead.
 14. The package of claim 8, further including: an electronicdevice mounted to a mounting portion of said lead frame, wherein saidmounting portion is separated from said lead and a portion of said leadproximal to said mounting portion is substantially free of metalplating; wires bonded from landing pads on said electronic device to ametal plate covered portion of said lead; and an insulating moldcovering said electronic device and said mounting portion of said leadframe.